Built an HTML sitemap in 2 hours. Indexing jumped.

Built an HTML sitemap in 2 hours. Indexing jumped.
Everyone says HTML sitemaps are dead. They're not — they're a crawl path, not a ranking page.
Client had 4,000 deep products, XML sitemap submitted, but ~30% never got crawled because nothing linked to them.
The move:
— Generated one HTML page: categories as headers, every product as a plain <a href> under its category.
— Linked it once from the footer. That's it.
— Now there's a 2-click crawl path from home to every single page. The crawler follows links, not XML wishes.
— Within 6 weeks, indexed pages climbed and deep products started ranking.
Watch the size. If you've got 50,000 URLs, paginate or split the HTML sitemap by category. One page with 50k links is a crawl trap of its own. Cap it around 200-300 links per page.